Renal Doppler-Based Assessment of Regional Organ Perfusion in the Critically Ill Patient

摘要

To the Editor: We read with great interest the manuscript by Li et al. (1) which underline that the fluid strategy in patients with septic shock remains one of unresolved pillars in intensive care unit. In critically ill patients, splanchnic Doppler, combining splenic and renal, has been recently proposed as a sensitive diagnostic and monitoring tool to assess and monitor hemody-namic (2). In particular, Doppler resistive index allows a non-invasive study of splanchnic circulation in response to pathological conditions. The lack of correlation with dynamic measures of fluid responsiveness and with a single hemodynamic variable has been raised as a potential concern. Renal perfusion may depend on a number of factors, including age, pre-existing comorbidities (potentially influencing arterial compliance/stiffness), vasopressor use, and positive pressure ventilation (3). Likewise, arterial renal Doppler resistive index (RDRI) is influenced by systemic vascular parameters, explaining the poor correlation with a single hemodynamic variable, and by the organ-specific vascular stiffness/compliance (4). On the mechanistic view arterial RDRI could be ideally considered as reflective of the actual organ perfusion contextualized with patient's conditions and hemodynamic profile. The limitation is that, although it may suggest the inappropriate perfusion of the organ, it is not helpful in identifying the underlying cause (low output or overload). However, venous renal Doppler has shown a strong correlation with organ congestion before adverse changes in cardiac filling pressure (5), although it has to be confirmed in critically ill population (being one of the RDRI research priorities). Putting all together, arterial RDRI may be helpful in detecting organ hypoperfusion and venous, potentially, to define the organ congestion (Fig. 1).